Acid Sulphate Investigations

Acid sulphate soils (ASS) are soils and sediments that contain iron sulphides, commonly pyrite. When exposed to air due to drainage or disturbance these soils produce sulphuric acid, often releasing toxic quantities of iron, aluminium and heavy metals. These chemicals can leach into waterways, kill fish, other aquatic life and vegetation, and can even damage concrete and steel pipes and structures to the point of failure. Acid sulphate soils are benign when in a waterlogged environment but become a serious problem when drained or excavated.

Acid sulphate soils are formed when seawater or other sulphate-rich water (e.g. some types of groundwater) mixes with sediments containing iron oxides and organic matter under waterlogged, anaerobic (oxygen free) conditions. The sulphides produced are stable until exposed to air at which point they produce sulphuric acid. Typically such soils are found in areas of low elevation but not always. They can be found at much higher elevations and also inland from the coast where ever the pyrite-forming conditions are found. Acid Sulphate Investigations involve sampling to determine the extent of the problem and for the purpose of specialised laboratory testing.

Acid Sulphate Soil and Water Management:

A formal Management Plan will be required if Acid Sulphate soils are present. The client may deal with this themselves via their Builder or Engineer OR if they require us to organise one, we can arrange for the production of a Management Plan Report suitable for the particular job.

Removal of soil from the site is not a viable option as it takes the problem elsewhere. Onsite treatment is the prime option. Close attention to draining is required.